London has been battered by 50mph winds that have felled trees and caused travel chaos. Powerful gusts swept across the capital as the Met Office issued a yellow "be aware" weather alert for most of the country.

Five high street banking giants have been ordered to raise another £13.4 billion to plug a higher-than-expected £27.1 billion hole in their finances.

The Prudential Regulation Authority (PRA) confirmed that Barclays, Lloyds Banking Group, Royal Bank of Scotland, Nationwide building society and The Co-operative Bank must take action to boost their balance sheets after uncovering the shortfall.

The institutions have already discussed plans with the PRA to tackle more than half - £13.7 billion - of the gap in their capital cushions, but they must stump up the remainder by the end of 2013 or early 2014.

The total combined shortfall is the amount banks need to raise in order to ensure their balance sheets are healthy enough to withstand future financial shocks and prevent a repeat of the banking meltdown in 2008.

As of the end of 2012, Barclays faced a £3 billion capital shortfall, while state-backed players RBS and Lloyds needed to raise £13.6 billion and £8.6 billion respectively - accounting for more than 90% of the overall blackhole between them.

Nationwide building society was found to be £400 million shy, while The Co-operative must stump up £1.5 billion as already announced. HSBC, Standard Chartered and Santander UK were given a clean bill of health.

The PRA said that after taking account of plans to fill the gap, Lloyds still needs to raise £7 billion, RBS £3.2 billion and Barclays £1.7 billion.

Measures to bolster the Co-op Bank's capital reserves were announced earlier this week, with bondholders forced to take losses on their investment as part of a complex "bail-in'' due to happen in October, which will result in a stock market listing for the UK's biggest mutual.

Nationwide said its "modest" shortfall was already accounted for in its 2013 financial plan. But the PRA said Nationwide and Barclays must also raise additional capital to reduce their leverage and must submit their proposals by the end of the month. Barclays, Lloyds and RBS said they were confident in their ability to meet the PRA's requirements.

The PRA said it has asked firms to ensure that all plans to address shortfalls do not reduce lending to the real economy, but there are fears the tough rules will hamper their ability to lend at a crucial time for the wider economic recovery. Kevin Burrowes, UK financial services leader at PricewaterhouseCoopers, said: "While more transparency is welcome, it is debatable whether this disclosure is supportive of pushing economic growth or facilitates more bank lending."